I have a international trip coming up to paris on United from ORD and onward trips to India on Lufthansa. So i tried searching for how to get complimentary upgrade on UA/LH legs. After much research i found that on european legs i m not able to get CPU and require a GPU and also some restrictions apply.

Now my question is is it a viable option to ask a United agent at the airport to ask for upgrade if the business or first lass seats are not filled up, or you wont get at all these upgrades irrespective of your platinum status.

Highly appreciate if some one can shed some light on this.